Regex rule: | -token doesn't work

Using the |-token in a regex rule breaks the rule and causes an error.

Error example:
"regex:EN|NO"
The rule is interpreted as NO being a seperate, invalid, rule

Possible fix:
Custom rule parsing, change regex parameter syntax to /[regex]/, ignore |'s between / /
e.g. "regex:/EN|NO/"

Start by locating the regex rule parser and any tests for rule syntax; the issue identifies the pipe in `regex:EN|NO` as being split into a separate rule. Done means regex alternatives such as `EN|NO` are accepted without treating `NO` as an invalid rule.

Written by the indexing model from the issue text.